ORCID Profile
0000-0002-1691-1648
Current Organisation
University of Aberdeen
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Publisher: MDPI AG
Date: 22-08-2022
DOI: 10.3390/EN15166086
Abstract: In this paper, a thorough framework for multiobjective design optimization of switched reluctance motor (SRM) is proposed. Selection of stator and rotor pole embrace coefficients is an essential step in the SRM design process since it influences torque output and torque ripple in SRM. The problem of determining optimal pole embrace is formulated as a multi-objective optimization problem with the objective of optimizing average torque, efficiency and torque ripple, and response surface models were obtained based on the genetic aggregation method. The results obtained by genetic aggregation response surface (GARS) and the non-dominated genetic algorithm (NSGA-II) were validated with the finite element method (FEM) model of the initial SRM. The optimized model displayed better efficiency profile over a wide speed range. The initial and optimized models recorded maximum efficiencies of 85% and 94.05%, respectively, at 2000 rpm. The efficiency values of 93.97–94.05% were achieved for the three pareto optimal candidates. The findings indicate the viability of the suggested strategy and support the use of GARS and NSGA-II as useful methods for addressing SRM key challenges.
Publisher: Institution of Engineering and Technology (IET)
Date: 2007
DOI: 10.1049/MNL:20065075
Publisher: Elsevier BV
Date: 08-2019
DOI: 10.1016/J.ISATRA.2019.01.028
Abstract: The fast and accurate tracking of periodic and arbitrary reference trajectories is the principal goal in many nanopositioning applications. Flexure-based piezoelectric stack driven nanopositioners are widely employed in applications where accurate mechanical displacements at these nanometer scales are required. The performance of these nanopositioners is limited by the presence of lightly d ed resonances in their dynamic response and actuator nonlinearities. Closed-loop control techniques incorporating both d ing and tracking are typically used to address these limitations. However, most tracking schemes employed use a first-order integrator where a triangular trajectory commonly used in nanopositioning applications necessitates a double integral for zero-error tracking. The phase margin of the d ed system combined with the hardware-induced delay deem the implementation of a double-integrator unstable. To overcome this limitation, this paper presents the design, analysis and application of a new control scheme based on the structure of the traditional Two-Degrees-of-Freedom PID controller (2DOF-PID). The proposed controller replaces the integral action of the traditional 2DOF-PID with a double integral action (2DOF-PI
Publisher: Frontiers Media SA
Date: 03-2016
Publisher: IOP Publishing
Date: 11-06-2015
Publisher: Elsevier BV
Date: 2014
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2012
Publisher: MDPI AG
Date: 30-12-2022
Abstract: Finding a reliable approach to detect bearing faults is crucial, as the most common rotating machine defects occur in its bearings. A convolutional neural network can automatically extract the local features of the mechanical vibration signal and classify the patterns. Nevertheless, these types of networks suffer from the extraction of the global feature of the input signal as they utilize only one scale on their input. This paper presents a method to overcome the above weakness by employing a combination of three parallel convolutional neural networks with different filter lengths. In addition, a bidirectional gated recurrent unit is utilized to extract global features. The CWRU-bearing dataset is used to prove the performance of the proposed method. The results show the high accuracy of the proposed method even in the presence of noise.
Publisher: IEEE
Date: 30-05-2021
Publisher: IEEE
Date: 05-2012
Publisher: Elsevier BV
Date: 10-2020
Publisher: IEEE
Date: 2009
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2014
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2008
Publisher: IEEE
Date: 22-08-2023
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2023
Publisher: IEEE
Date: 08-2020
Publisher: IEEE
Date: 05-2009
Publisher: IEEE
Date: 19-02-2023
Publisher: IEEE
Date: 07-2015
Publisher: IEEE
Date: 09-2015
Publisher: Elsevier BV
Date: 07-2022
Publisher: IEEE
Date: 07-2007
Publisher: Elsevier BV
Date: 09-2014
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2021
Publisher: IEEE
Date: 04-2011
Publisher: Elsevier BV
Date: 11-2023
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2019
Publisher: OSA
Date: 2018
Publisher: MDPI AG
Date: 22-01-2018
Publisher: SAGE Publications
Date: 22-08-2019
Abstract: Nanopositioners are mechanical devices that can accurately move with a resolution in the nanometer scale. Due to their mechanical construction and the piezoelectric actuators popularly employed in nanopositioners, these devices have severe performance limitations due to resonance, hysteresis and creep. A number of techniques to control nanopositioners, both in open-loop and closed-loop, have been reported in the literature. Closed-loop techniques clearly outperform open-loop techniques due to several desirable characteristics, such as robustness, high-bandwidth, absence of the need for tuning and high stability, along with others. The most popular closed-loop control technique reported is one where a d ing controller is first employed in an inner loop to d the mechanical resonance of the nanopositioner, thereby increasing achievable bandwidth. Consequently, a tracking controller, typically an Integral controller or a proportional–integral controller, is implemented in the outer loop to enforce tracking of the reference signal, thereby reducing the positioning errors due to hysteresis and creep dynamics of the employed actuator. The most popular trajectory a nanopositioner is forced to track is a raster scan, which is generated by making one axis of the nanopositioner follow a triangular trajectory and the other follow a slow r or staircase. It is quite clear that a triangle wave (a finite velocity, zero acceleration signal) cannot be perfectly tracked by a first-order integrator and a double integrator is necessary to deliver error-free tracking. However, due to the phase profile of the d ed closed-loop system, implementing a double integrator is difficult. This paper proposes a method by which to implement two integrators focused on the tracking performance. Criteria for gain selection, stability analysis, error analysis, simulations, and experimental results are provided. These demonstrate a reduction in positioning error by 50%, when compared to the traditional d ing plus first-order integral tracking approach.
Publisher: IOP Publishing
Date: 07-09-2022
Abstract: Dielectric elastomer actuators (DEAs) usually suffer from rate-dependent viscoelastic nonlinearity, which manifests as hysteresis in their deformation cycles, leading to huge challenges in their modeling and control. In this work, we propose a model-free, proxy-based, sliding-mode tracking control approach to mitigate viscoelastic nonlinearity, achieving high-precision tracking control of DEAs. To this end, we first investigate the viscoelastic nonlinearity of DEAs, revealing its asymmetric and rate-dependent characteristics. Then, by combining the benefits of the PID control for small positioning errors and sliding-mode control for large errors, a proxy-based, sliding-mode tracking controller (PBSMC) is established. Finally, the stability of the controller is analyzed. To verify the effectiveness of the controller, several experiments are conducted to demonstrate the performance of DEAs in tracking sinusoidal trajectories under different frequencies. The experimental results demonstrate that with the PBSMC, the DEA can precisely track sinusoidal trajectories within a frequency range of 0.1 Hz–4.0 Hz by effectively minimizing the effect of inherent viscoelastic nonlinearity. Compared with open-loop tracking performance, the proxy-based, sliding-mode controlled DEA shows a significant reduction in maximum tracking errors from 45.87% to 8.72% and in root-mean-square errors from 24.46% to 3.88%. The main advantages of the proxy-based, sliding-mode control are: (a) it adopts a model-free approach, avoiding the need for complex dynamic modeling (b) it can achieve high-precision tracking control of DEAs, thereby paving the way for the adoption of DEAs in several emerging applications.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2009
Publisher: Institution of Engineering and Technology (IET)
Date: 02-2017
Publisher: Elsevier BV
Date: 2021
Publisher: IEEE
Date: 07-2013
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2011
Publisher: IEEE
Date: 06-2019
Publisher: Elsevier BV
Date: 07-2017
Publisher: IEEE
Date: 22-11-2022
Publisher: IEEE
Date: 06-2019
Publisher: Institution of Engineering and Technology (IET)
Date: 12-2020
Publisher: Elsevier BV
Date: 2021
Publisher: Elsevier BV
Date: 08-2022
Publisher: IEEE
Date: 10-2017
Publisher: IEEE
Date: 2009
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2023
Publisher: ACTAPRESS
Date: 2016
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2011
Publisher: MDPI AG
Date: 29-06-2021
DOI: 10.3390/MATH9131526
Abstract: Friction-induced stick-slip vibrations are one of the major causes for down-hole drill-string failures. Consequently, several nonlinear models and control approaches have been proposed to solve this problem. This work proposes a dual-loop control strategy. The inner loop d s the vibration of the system, eliminating the limit cycle due to nonlinear friction. The outer loop achieves the desired velocity with a fast time response. The optimal tuning of the control parameters is carried out with a multi-method ensemble meta-heuristic, the Coral Reefs Optimisation algorithm with Substrate Layer (CRO-SL). It is an evolutionary-type algorithm that combines different search strategies within a single population, obtaining a robust, high-performance algorithm to tackle hard optimisation problems. An application ex le based on a real nonlinear dynamics model of a drill-string illustrates that the controller optimised by the CRO-SL achieves excellent performance in terms of stick-slip vibrations cancellation, fast time response, robustness to system parameter uncertainties and chattering phenomenon prevention.
Publisher: IEEE
Date: 22-08-2022
Publisher: MDPI AG
Date: 29-11-2022
Abstract: This paper presents a method to extend the eigenstructure assignment based design of the Positive Position Feedback (PPF) d ing controller to the family of well-known second-order Positive Feedback Controllers (PFC) namely: (i) the Positive Velocity and Position Feedback (PVPF) and (ii) the Positive Acceleration Velocity and Position Feedback (PAVPF) using appropriate eigenstructure assignment. This design problem entails solving a set of linear equations in the controller parameters using Linear Matrix Inequalities (LMI) to specify a convex design constraint. These d ing controllers are popularly used in tandem with a tracking controller (typically an integrator) to deliver high-bandwidth nanopositioning performance. Consequently, the closed-loop performance of all three controllers (PPF, PVPF and PAVPF) employed in tandem with suitably gained integral tracking loops is thoroughly quantified via relevant performance metrics, using measured frequency response data from one axis of a piezo-stack actuated x-y nanopositioner.
Publisher: MDPI AG
Date: 11-01-2019
Abstract: Tracking triangular or staircase trajectories is a challenge for a piezo-driven nanopositioner due to vibration problems. The piezo-driven nanopositioner is a lightly-d ed system because of its mechanical construction. These reference trajectories are high-frequency components that tend to excite the mechanical resonance of the nanopositioner, causing vibration and thus affecting the accuracy. The Integral Resonant Controller (IRC) is employed to d the resonance and thereby furnish a larger gain margin for a high-gain tracking controller to be implemented. The IRC, however, introduces a low-frequency pole. Due to other control issues, such as hysteresis nonlinearity, Integral (I) or Proportional Integral (PI) tracking control is used as a tracking loop to address uncertainties (hysteresis). The traditional method using a PI controller has a limited positioning bandwidth. This paper presents the strategic zero placement of the PI controller to enhance the positioning bandwidth, thereby overcoming the limitations of tracking error. Using experimental validations to confirm the feasibility of the proposed method, it is shown that significant improvement regarding bandwidth and disturbance rejection are reported.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2021
Publisher: IOP Publishing
Date: 09-02-2007
Publisher: ACTAPRESS
Date: 2016
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2010
Publisher: ACTAPRESS
Date: 2016
Publisher: Elsevier BV
Date: 2014
Publisher: SPIE
Date: 06-04-2007
DOI: 10.1117/12.715477
Publisher: Springer Singapore
Date: 2017
Publisher: ACTAPRESS
Date: 2016
Publisher: Elsevier BV
Date: 11-2018
DOI: 10.1016/J.ISATRA.2017.09.022
Abstract: By exploiting the co-located sensor-actuator arrangement in typical flexure-based piezoelectric stack actuated nanopositioners, the polezero interlacing exhibited by their axial frequency response can be transformed to a zero-pole interlacing by adding a constant feed-through term. The Integral Resonant Control (IRC) utilizes this unique property to add substantial d ing to the dominant resonant mode by the use of a simple integrator implemented in closed loop. IRC used in conjunction with an integral tracking scheme, effectively reduces positioning errors introduced by modelling inaccuracies or parameter uncertainties. Over the past few years, successful application of the IRC control technique to nanopositioning systems has demonstrated performance robustness, easy tunability and versatility. The main drawback has been the relatively small positioning bandwidth achievable. This paper proposes a fractional order implementation of the classical integral tracking scheme employed in tandem with the IRC scheme to deliver d ing and tracking. The fractional order integrator introduces an additional design parameter which allows desired pole-placement, resulting in superior closed loop bandwidth. Simulations and experimental results are presented to validate the theory. A 250% improvement in the achievable positioning bandwidth is observed with proposed fractional order scheme.
Publisher: Informa UK Limited
Date: 03-2013
Publisher: Springer Singapore
Date: 2017
Publisher: Springer Singapore
Date: 2017
Publisher: MDPI AG
Date: 22-10-2020
DOI: 10.3390/ACT9040108
Abstract: In many applications comprised of multiple platforms with stringent vibration isolation requirements, several vibration isolators are employed to work in tandem. They usually must accomplish two objectives: (i) reduce the vibration level of each platform and (ii) maintain the required alignment with respect to each other or with a fixed reference. If the isolators are located on a rigid supporting structure, the problem can be approached as a classical vibration isolation (VI) problem, in which an increase in d ing implies a reduction of vibration level experienced by the platforms. However, there are an increasing number of scenarios in which the dynamic interaction between the isolator and the base structure has the potential to alter the system response and consequently degrade VI performance. In this work, a generalized method to analyze the combined VI and alignment problem, for multiple isolators located on a flexible supporting structure, is proposed. The dynamic interaction between the platforms and the isolators is considered in the control design, and it is proved employing two different functional values that the maximum d ing solution is not always the best approach when the dynamics of the supporting structure are considered. Numerical simulations are presented to validate the theory developed and robustness of the proposed control approach is demonstrated.
Publisher: IEEE
Date: 22-08-2022
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2019
Publisher: ACTAPRESS
Date: 2016
Publisher: Elsevier BV
Date: 05-2020
Publisher: IEEE
Date: 08-07-2023
Publisher: Elsevier BV
Date: 2014
Publisher: IOP Publishing
Date: 20-02-2008
DOI: 10.1088/0957-4484/19/12/125503
Abstract: Inversion-based feedforward techniques have been known to deliver accurate tracking performance in the absence of plant parameter uncertainties. Piezoelectric stack actuated nanopositioning platforms are prone to variations in their system parameters such as resonance frequencies, due to changes in operating conditions like ambient temperature, humidity and loading. They also suffer from nonlinear effects of hysteresis, an inherent property of a piezoelectric actuator charge actuation is applied to reduce the effects of hysteresis. In this work, we propose and test a technique that integrates a suitable feedback controller to reduce the effects of parameter uncertainties with the inversion-based feedforward technique. It is shown experimentally that the combination of d ing, feedforward and charge actuation increases the tracking bandwidth of the platform from 310 to 1320 Hz.
Publisher: IEEE
Date: 2003
Publisher: IOP Publishing
Date: 06-11-2008
Publisher: MDPI AG
Date: 20-09-2022
Abstract: Designers of Positive Feedback Controllers (PFCs) arbitrarily place poles into the left-hand half-plane of the complex plane without any detailed understanding of where to stop. This works aims to clearly demonstrate, via rigorous mathematical derivation, the conditions for which pole–placement becomes possible. It also highlights the design limits for the family of second–order PFCs—the most popular PFC group. To this end, the complete family of PFCs, namely, Positive Acceleration Velocity Position Feedback and its derivatives, are analysed in great depth with respect to pure d ing and also with respect to combined d ing and tracking applications. To showcase the practical value and validity of this work, experimental results on a piezoelectric nanopositioner are also presented and discussed.
Publisher: Springer Science and Business Media LLC
Date: 22-06-2023
Publisher: Elsevier BV
Date: 07-2017
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2021
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2021
Publisher: Elsevier BV
Date: 05-2023
DOI: 10.1016/J.ISATRA.2022.10.028
Abstract: This paper presents a new Global Fast Non-singular Terminal Sliding Mode Controller (GFNTSMC) that delivers high-precision tracking of high-frequency trajectories when applied to a piezo-driven nanopositioner. The control scheme is realized by combing inverse hysteresis model and global fast non-singular terminal sliding mode compensation. The inverse Bouc-Wen hysteresis model is used to calculate the required hysteresis-compensating feedforward control voltage according to the reference signal. The key uniqueness of the proposed control strategy is it's red global fast convergence, achieved with high accuracy and high bandwidth. The stability of the reported GFNTSMC controller is proved with the Lyapunov theory. Its performance is verified through experimentally recorded tracking results, and its superiority over three benchmark control approaches, namely the Proportional-Integral-Derivative (PID), the Positive Position Feedback with integral action (PPF+I) and the conventional linear high-order sliding mode controller (LHOSMC) is demonstrated through comparative tracking error analysis. Its wide-band stability as well as its significant robustness to parameter uncertainty is also showcased.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2020
Publisher: Springer Science and Business Media LLC
Date: 05-03-2021
DOI: 10.1007/S11465-020-0619-X
Abstract: Typically, the achievable positioning bandwidth for piezo-actuated nanopositioners is severely limited by the first, lightly-d ed resonance. To overcome this issue, a variety of open- and closed-loop control techniques that commonly combine d ing and tracking actions, have been reported in literature. However, in almost all these cases, the achievable closed-loop bandwidth is still limited by the original open-loop resonant frequency of the respective positioning axis. Shifting this resonance to a higher frequency would undoubtedly result in a wider bandwidth. However, such a shift typically entails a major mechanical redesign of the nanopositioner. The integral resonant control (IRC) has been reported earlier to demonstrate the significant performance enhancement, robustness to parameter uncertainty, guaranteed stability and design flexibility it affords. To further exploit the IRC scheme’s capabilities, this paper presents a method of actively shifting the resonant frequency of a nanopositioner’s axis, thereby delivering a wider closed-loop positioning bandwidth when controlled with the IRC scheme. The IRC d ing control is augmented with a standard integral tracking controller to improve positioning accuracy. And both d ing and tracking control parameters are analytically optimized to result in a Butterworth Filter mimicking pole-placement—maximally flat passband response. Experiments are conducted on a nanopositioner’s axis with an open-loop resonance at 508 Hz. It is shown that by employing the active resonance shifting, the closed-loop positioning bandwidth is increased from 73 to 576 Hz. Consequently, the root-mean-square tracking errors for a 100 Hz triangular trajectory are reduced by 93%.
Publisher: Elsevier BV
Date: 08-2020
Publisher: Elsevier BV
Date: 08-2021
Publisher: Springer Science and Business Media LLC
Date: 10-11-2020
DOI: 10.1007/S11012-020-01264-5
Abstract: Despite a significant research effort to understand and mitigate stick-slip in drill-strings, this problem yet to be solved. In this work, a comprehensive parametric robustness analysis of the sliding mode controller has hitherto been performed. First, a model verification and extensive parametric analysis of the open-loop model is presented. This is followed by a detailed parametric analysis of the sliding-mode controller based closed-loop system for two cases, (i) an ideal actuator with no delay or constraint and (ii) a realistic actuator with delay or/and constraint. It is shown that though the proposed controller works robustly across a wide range of parameters, in the absence of delay, it fails in the presence of a delay, thereby limiting its practical application. Experimental results are included to support these claims. This work underlines the importance of including the inherent system characteristics during the control design process. Furthermore, the parametric analysis presented here is aimed to act as a blue-print for testing the efficacy of relevant control schemes to be proposed in the future.
Publisher: IEEE
Date: 07-2008
Publisher: IEEE
Date: 07-2008
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2009
Publisher: ASME International
Date: 10-07-2015
DOI: 10.1115/1.4030723
Abstract: Positive velocity and position feedback (PVPF) is a widely used control scheme in lightly d ed resonant systems with collocated sensor actuator pairs. The popularity of PVPF is due to the ability to achieve a chosen d ing ratio by repositioning the poles of the system. The addition of a tracking controller, to reduce the effects of inherent nonlinearities, causes the poles to deviate from the intended location and can be a detriment to the d ing achieved. By designing the PVPF and tracking controllers simultaneously, the optimal d ing and tracking can be achieved. Simulations show full d ing of the first resonance mode and significantly higher bandwidth than that achieved using the traditional PVPF design method, allowing for high-speed scanning with accurate tracking. Experimental results are also provided to verify performance in implementation.
Publisher: Elsevier BV
Date: 06-2013
Publisher: Elsevier BV
Date: 12-2013
Publisher: Springer Singapore
Date: 2017
Publisher: Springer International Publishing
Date: 07-10-2022
Publisher: Wiley
Date: 07-12-2023
DOI: 10.1002/RNC.6526
Abstract: For high‐performance trajectory tracking at the nanometer scales, this paper presents a new fast terminal sliding mode controller, which combines a recursive integer‐order non‐singular high‐order sliding manifold and a fractional‐order fast fixed‐time reaching law to ensure globally fast convergence, and adopts a time‐delay‐estimation (TDE) based disturbance estimator deeming the designed controller robust to parameter uncertainty. Stability of the designed controller is verified through the Lyapunov framework, where the full analyses of convergence region and settling time are also presented. The tracking performance is experimentally verified on a piezo‐stack driven nano‐positioning platform. To showcase the performance improvements, measured closed‐loop performance of the proposed controller is contrasted with those obtained using three benchmark control approaches namely the basic Proportional‐Integral‐Derivative (PID), the popular Positive Position Feedback with Integral action (PPF+I), and the traditional linear sliding mode controller (LSMC).
Publisher: Springer International Publishing
Date: 07-10-2022
Publisher: IEEE
Date: 26-11-2022
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Sumeet Aphale.